1. Field of the Invention
This invention relates to a memory system of wheel speed of a vehicle with skid control system, and more particularly to a memory system for memorizing accurately the wheel speed of the vehicle with skid control system even in an accident or an emergency in which the vehicle does not leave tire traces on the road, even when the vehicle is rapidly braked, due to skid control operation.
2. Description of the Prior Art
Hitherto, a tachograph is used as a recorder in which a vehicle speed or a wheel rotational speed is always recorded. It is suitable for rough check of change of wheel speed. However, it is unsuitable for the case that the change of wheel speed for a very short time in an emergency or an accident should be investigated, or that brake operation immediately before the emergency or accident should be investigated, since its resolving power is poor.
Generally, when a vehicle with skid control system is rapidly braked, the skid control system operates. Accordingly, such an apparatus was already proposed that an operation signal or control signal from the skid control system is recorded in order to know how the vehicle has been braked. However, when a vehicle runs on a road of high frictional coefficient, a large braking force can be imparted to the vehicle without skid. The skid control system does not operate, although a sufficient braking operation has been performed. In that case, it is unknown whether any braking operation has been performed, or not, from the recorder. There is the fear of misjudgement.